For countless fans of diesel, the brand “Cummins” has been the first name in diesel for decades. Since its founding over a century ago, diesel was the core of Cummins’ business. But now, Cummins has done something weird. Last week, the company announced its first gasoline engine. That’s weird enough, but Cummins says that its new B6.7 Octane engine is based on the legendary 6.7-liter diesel engine and all of this is actually pretty smart.
The modern diesel engine is a mechanical marvel. Today you can buy pickup trucks with glorious engines that pump out over 1,000 lb-ft of stump-pulling power. These same engines can also return fuel economy into the 20-mpg range even though the trucks they’re bolted to weigh as much as the Chrysler Building.
But the modern diesel has also lost its edge. Buying a diesel used to mean saving money at the pump and an engine so durable it could outlast humanity. However, diesel fuel is now more expensive than gasoline. Couple that with the higher costs of maintaining modern diesel emissions equipment, and diesel engines are making less sense with each passing year.
California and other states are also pumping the brakes on diesel with strict emissions regulations. Despite all this, diesel power still has a solid footing in several industries. The massive diesel engines that power locomotives, large generators, construction equipment, and highway semi-tractors remain the kings of their segments. Diesel also still has its place in heavy-duty pickup trucks.
But what if you could have it all? What if you could have an engine with easier maintenance and fewer emissions equipment needs that go with gasoline consumption, while delivering the durability and power of a diesel? That’s more or less what Cummins is pitching with its new B6.7 Octane gasoline engines. By starting out with a diesel engine platform and adapting it to gasoline, Cummins believes it has created the ultimate workhorse.
The B6.7 Octane has a lot going for it on paper. It runs on 87 octane pump gas and has the potential to breathe some new life into internal combustion in commercial vehicles. From my seat here, I also see the B6.7 Octane as a potential solution to the California regulations that may kneecap diesel motorhome sales this year. Many of these coaches could get Cummins gasoline power!
It’s amazing that Cummins, founded in 1919, has gone this long without making a single production gasoline engine. The history of Cummins is chock-full of great diesel feats and even some alternative fuels like propane and natural gas, but it might be shocking to read that Cummins is getting gasoline engines, something it’s not at all known for.
In 2022, Cummins launched what it called its “fuel-agnostic” engine strategy. According to trucking journal CCJ, the goal of the Cummins fuel-agnostic strategy is to create a bridge between the heavy diesel engines of today and the heavy electric motors of tomorrow. The company recognizes that electric power is not yet ready to take over from diesel, so until electric and battery tech reaches that point, Cummins wants to offer other ways of reducing emissions and operating costs in everything from school buses to highway tractors.
Cummins sees the fuel-agnostic strategy working for a variety of its engines ranging from Ram truck engines to the big boys you’ll see churning away in straight trucks and RVs. In 2022, it was expected that Cummins’ first engine based on this new architecture was to be based on the B6.7 diesel found in Ram pickups and medium-duty trucks. However, Cummins also wanted to apply the new tech to the L Series and X Series engines used in bigger rigs. The goal is that when a customer orders a truck with a Cummins engine, they’d get their choice of diesel, natural gas, hydrogen, propane, or gasoline. To be clear, these aren’t multi-fuel engines. Once you order your engine it runs only on whatever fuel you chose for it.
In 2024, Cummins renamed this project to “Higher Efficiency, Lower emissions and Multiple fuels,” or HELM, and it has the same goals as the fuel-agnostic engine project.
How it works is pretty neat. To create the new architecture, Cummins started with existing platforms. Cummins says that the components below the heads of the base engines are supposed to be similar across the lineup. In other words, the bits under the head of the B6.7 Octane should be bits largely similar to what you get in the B6.7 diesel straight-six that powers hundreds of thousands of trucks.
The parts commonality is pitched as not only a way for Cummins to make a variety of engines easier, but for fleet operators to have an easier time. In theory, a B6.7 Octane may have a similar diagnosis tree as a B6.7 diesel, at least under the head, anyway. Cummins also sees the B6.7 Octane as having diesel-like service intervals and saving fleets additional money as they won’t have to re-tool service departments just for the gasser.
Cummins is tight-lipped about the exact changes necessary to make the B6.7 platform to run gas, but thus far says that most of the changes are in the head. For now, Cummins really wants you to know how big of a deal the engine is:
The Cummins B6.7 Octane – Cummins’ first gasoline-powered engine is purpose-built to deliver the highest durability of any medium-duty gasoline engine on the market.
The Cummins B6.7 Octane engine is specifically designed and developed for the medium-duty market while achieving 2027 EPA and CARB compliance. Expanding the legacy of the Cummins B-series platform, the B6.7 Octane is equipped with the power, durability and performance of diesel with the simplicity of gasoline.
Cummins has also provided a handy sheet for both the gas and propane variants of the B6.7:
The company goes further and says this is the only purpose-built gasoline engine in the medium-duty truck market, and that it gets up to 10 percent better fuel economy than other gas engines in medium-duty trucks. The biggest advantage, Cummins says, will be in maintenance. The B6.7 Octane has passive catalysts for emissions controls, and that means no DPFs and no DEF to worry about anymore. According to Cummins, the engine should only require the kind of maintenance expected for a gas engine in a pickup truck.
This engine is also supposed to work a bit like a diesel. Cummins is currently quoting a maximum horsepower rating of 300 HP with max torque pegged at 660 lb-ft. Now, the truck engine nuts among you might find these numbers interesting. The horsepower rating is far lower than the 430 HP on tap in the Ford 7.3-liter Godzilla V8, but the twist in the Cummins is better than the Godzilla’s 475 lb-ft. Again, that’s by design. Like a common diesel engine, the Cummins straight-six gasser is supposed to make substantially more torque than horsepower.
Cummins also says it has been testing other power outputs, including 200 HP and 600 lb-ft of torque and 220 HP as well as 260 HP. Both of those latter power figures would also pump out 600 lb-ft of torque. However, the company says that aside from the max power figures, exact ratings have not been determined just yet.
Cummins says it’s also targeting the same transmissions found in medium-duty Cummins 6.7 diesel pairings, notably the Allison 2000 and 3000.
The company hopes to drop these engines into pickup trucks, school buses, step vans, delivery vehicles, and service trucks. For now, the launch customer is Kenworth and the truck maker says it’ll be putting these engines into Class 5 through 7 conventional trucks beginning sometime later this year. One early review seems to suggest that these engines do perform like diesels, too, which is awesome. Take a listen to that soundtrack! It’s like a diesel, but not:
That being said, I probably wouldn’t expect a 6.7 straight-six gasser to be around for a very long time. Cummins acknowledges that internal combustion engines might be living on borrowed time:
Cummins HELM platforms are a key component of a broader Destination Zero strategy. This ambitious plan focuses on achieving zero emissions by investing in cutting-edge technologies and improving internal combustion engines (ICE) to reduce emissions in the near term while preparing for a zero-emissions vehicle future.
Destination Zero is built on the understanding that decarbonization is a journey, and different industries and regions will move at different speeds. Cummins has adopted a balanced approach, continuing to enhance ICE technology for immediate gains in efficiency while also investing heavily in hydrogen fuel cells, battery electric systems, and other future technologies that will drive the transition to zero-emission vehicles.
As silly as all of this might sound, it’s actually not that crazy. Some might want to draw parallels to the 1970s when General Motors used gas engine architecture to create diesels. But that’s not the only time when an existing architecture running on a different fuel source was converted to something else. Notably, Kawasaki has been building prototype hydrogen engines out of the architecture of the gasoline H2 motorcycle engine.
This isn’t even the first time a Cummins has been made into a gas engine. Back in the 1960s, the White Motor Company was convinced that gasoline engines were the future, not diesel. In response, the company took 500 cubic inch Cummins diesel engines and converted them to gasoline. The “Giesel” and the White Trucks Mustang VIII, as they were called, allegedly used lower compression pistons and placed spark plugs where the diesel injectors used to live.
Cummins is technically correct when it calls the B6.7 its first gasoline engine since White converted the Cummins engines into gasoline, not Cummins.
As of right now, Cummins hasn’t made any mention about the future of where this engine could end up. The company figured it could put a 6.7 gasser into a pickup truck, but no official announcement about that exists at this time. But if this goes well, who knows where we could see these engines.
Images: Manufacturers
Top graphic images: Cummins; Wavian USA
I saw this engine for the first time about 2 years ago when we did our first mock-up. I’m interested to see how it will do.
Gas engines have been increasing in popularity in the class 4 – 6 category for city based applications like ambulances, wreckers, box trucks as diesel emissions equipment struggle in heavy stop and go routes. We will see if the guys buying Freightliner M2 and International MV trucks are interested in a gas Cummins.
This is interesting, and of course (predictably) I’d like to see this in a CAR even though the economic/use case would be difficult to make. We don’t all lust for big pickups. 😉
Swap it into a 1970s luxury land yacht. Obscene torque at low RPMs going through a beefed up Torqueflight727 or TH400 or C6 into 2.5 gears.
Beyond my ability/expertise, but yes, that’s the idea. I was thinking the new/current Toyota Crown Signia would be nice w/a diesel 6 (or big 4) instead of the hybrid drivetrain (just fantasizing I know… there’d be no market for it at all).
I was always a bit sad that I never bought a B4 VW Passat TDI… those older ones with the really big fuel tank in the wagon (I think someone got just over 1,000 miles on a single tankful by hypermiling per Fred’s TDI Club forum). I did buy a Golf TDI and kept it for more than two decades, and liked it, but the VWishness of it when it got to be 20 years old really took the shine off of the ownership experience. It’s the only diesel vehicle I’ve owned thus far.
Sure, if you don’t mind having an engine that weighs half as much as the car. 300 hp is easy enough to achieve in a much smaller and lighter package.
Of course diesels tend to be heavier, what with their higher compression, added torque, etc… Some folks (myself included just enjoy the way it feels (felt, in my case) to drive a diesel vehicle, that’s all. I had a turbodiesel Golf for 23 years (an A4) and the engine was the best part of that car… I can’t imagine I’d have kept/driven a gas-fueled A4 Golf even half that long, as they’re pretty unremarkable. 🙂
For sure. The 1.9 TDi engine weighs only 360 lbs whereas the 6.7 Cummins engine weighs 1,071 lbs. Your Golf would not be nearly as enjoyable to drive with another 711 lbs in the front – though you would have another 270 hp…
There’s been a handful of gas/e85 conversions to 6BT engines that I’ve seen, it’s amazing they took this long to do this. Unfortunately, I saw them on Facebook, so I can’t find them right now.
I think they are smart to focus on medium duty trucks. I don’t think this is a good fit for light trucks (1500-3500). These engines are going to have pretty low power to weight ratio and they aren’t going to be great on fuel. Their main benefits will come from lower upfront costs and lower maintenance costs. I do have to wonder if the economies of scale will make up for the higher cost of a semi-common bottom end though, given that diesel engines require so much more strength for their higher cylinder pressures.
It will either be a great, long lived and well respecting working engine, or failed test of the fuel agnostic theory.
This needs swapped into a tesla.
“Most of the changes are in the head,” to wit: “we bored and tapped a hole for a spark plug.”
Cummins’ long experience with making diesels better – less noisy, less polluting, more flexible over a wider rev range etc etc etc, all work in favor for gasoline engines too. About the only thing I can think of stopping a diesel engine from being a good gas engine is the sky-high compression ratio, and with carefully modulated direct injection I think that wouldn’t be an issue, either.
Combustion chamber and piston design will have to be different, as well as the valves, valve springs and cam profile to have it run efficiently on gasoline. Basically a cam profile and top-end engineered for lower compression and spark ignition. I’d guess it’s a significantly re-engineered head and related components. The block, main bearings, crankshaft and flywheel can remain the same. Everything that bolts on can be made modular. The heavy-duty bottom-end may be overbuilt by today’s standards, but it will go a long way to forming the basis for a million-mile gas engine, something that’s largely gone extinct since the Ford 300 I6 and old IH V8 designs were retired.
I feel like a lot of the people who will get excited about this type of engine are going to be fleet managers, and a lot of them people in their 50s now who remember driving or riding vehicles powered by these kinds of slow-revving, torquey big engines that just worked hard with few complaints or breakdowns, and relatively straightforward repair/rebuilds. Yes, it’s probably “overbuilt”, but the efficiency is connected to the long return on investment. If repair costs are economical in terms of time and parts cost, scheduled maintenance intervals are good and don’t take a unit out of service for too long, and overhaul/rebuild is an economical alternative to replacement, then this engine will likely find a lot of acceptance in fleets.
Yeah, I’m being simplistic. I think your example of the Ford 300 is probably close to the example, a dogged and relentless mill that goes in today and goes on forever. It’ll be overbuilt, but that’s a small price to pay today for getting to pay less for everything for years afterward.
I’m thinking that with the diesel engine’s capacity to survive higher cylinder pressures, the SI engine could run higher compression than typical gas engines and soften the jolt with a small preliminary injection, and then ramp up pressure with additional injection events.
I also wonder about sufficient power overhead that a variable valve timing setup could Atkinson-ize the combustion cycle while still generating enough power for ultra-light loads like when deadheading.
What’s interesting is that somebody has finally decided to apply modern fuel injection and intake management technology to block design with roots in a much older era of heavy engine construction. It might seem odd to people accustomed to designs of the past 25 years or so, where engineering for light weight and adequate strength has been the rule. But we’ve also seen that lead to engines that are fantastic until it’s time for repair or overhaul, and then costs can spiral up. It doesn’t make that much difference for someone’s daily driver pickup that will never rack up the annual mileage of a fleet truck. But for fleets, it’s a whole different story for cost management.
Needs an aluminum block or it’s going to weight 900 lbs.
My guess is that the “smallest” truck it would fit in would be a full-size one-ton truck, just like putting the Cummins ISB in a Ram 2500, just due to packaging issues alone.
Bread-and-butter uses are more likely to be in school buses, other types of smaller buses, and various types of delivery trucks, where reliability and good power/efficiency is more important than weight savings for total payload capacity. Vehicles which are loaded to passenger or cubic volume capacity more so than weight capacity and expected to get out and make money with minimal downtime. As long as overall operating efficiency meets expectations, the weight of the engine and entire drivetrain isn’t as big of a concern.
And for a “bread truck” style delivery van, having plenty of engine weight at the front axle is a good offset where the loading is often spread wide and high using cargo shelves and racks; the rear axle loading and sometimes high CG benefits from keeping a bit more weight in front.
Gotta beef it up with thicker walls though. The sharper pressure rise of gasoline ignition makes for a lot of bad shock loading, and aluminum fatigues way, way worse than iron.
The head is a different part from the diesel version, so I doubt there’s any problem accomplishing that.
I think that’s the point. It’s for vehicles that already weigh a lot and with big payloads, so saving a few hundred pounds in the engine compartment isn’t critical. The longevity will be greatly increased.
I’m sure it’s well over 1000 pounds, just like its diesel counterpart…but it doesn’t matter in those applications.
A Cummins engine running on guzzoline? They shoulda called it the Cummins Guzzler!
Cummins, Jake brake, and the mechanism that keeps your drill bit connected to your drill (the chuck?) are all related. It should be a movie.
Important info missing: how much does it cost?
It doesn’t sound like this is a consumer product, although it’s possible they’ll sell replacement crate engines to the public. Cummins generally manufactures engines for other companies that build the trucks, generators, heavy equipment, etc. Details of each contract are unlikely to be made public but I would imagine Cummins is trying to keep the unit cost as close as possible to the original diesel engine but it will likely be higher, possibly with different pricing based on fuel options.
Cummins offers a number of engines for retrofitting.
Some delivery vans can be ordered from major companies, and a 4 cylinder Cummins is offered to plug and play for the chosen brand.
Some insane transmission options will attach to a Cummins pickup engine.
King of retrofitting in many cases.
I’m thinking a heavy 8 speed manual would hold up well in a 4 ton truck.
The V8 was supposed to be offered as a Repower engine as well, until the entire line was axed.
My question was more like if I’m purchasing a fleet of vehicles from an OEM, how does the Cummins gasser price compare to a 7.3 Ford gasser, and how much longer is the useful life. Does it have a real business case?
No idea how Ford pricing is these days.
I have the all iron Cummins.
If it’s built to those specs, I would expect a considerably higher price.
Major parts are likely expensive, but nearly everything is rebuildable on mine.
No one knows end of life on my engine, but it would measure in millions of miles.
Used in boats, where they typically run full power, rebuilds are set for 15,000 hours.
Sadly, that data has not been released yet!
Since these are tuned for tons of torque, they should be pretty efficient when they’re not being over-revved.
Do they quote an RPM range? If this thing can turn high RPM, it might be made into a monster.
From the numbers (HP < torque) and the commentary (drop in replacement), it’s the same RPM range as the diesel version. The heavy conrods are going to limit RPMs a lot. But who knows what you could do to one if you weren’t trying to get 1M miles out of it?
That seems odd to me, as RPM is limited in a diesel engine due to the time it takes to burn the fuel. Carrying that limitation over to the gasoline version solely in the name of longevity seems like a stretch.
But you may very well be right, as they are talking about carry over transmissions. I’m interested to see what rpm range this really has.
I bet David is really jealous that you scooped him on this news.
Great job Mercedes!
I know it was muffled and potato-mic’d but that sounded pretty good! I’ll miss (muffled) diesel sounds and (appropriately filtered) diesel smells, but not so much that I won’t be cheering for the end of the 130dB soot-cloud jackoff-mobiles. At the very least the soot cloud will go away.
Well tuned diesels have clear exhaust.
Most drivers aren’t idiots.
Same for noise.
Every like 2 months here in the Midwest I’ll see a Super Duty or something that has been tastefully modified and doesn’t emit a speck of soot when the driver gets on it. It’s like briefly glimpsing an alternate dimension when the veils between realities grow thin.
Well engineered hot rods tend to not draw much attention.
Wasted fuel is wasted power.
“Cummins is currently quoting a maximum horsepower rating of 300 HP with max torque pegged at 660 lb-ft”
That just sounds like they are keeping the diesel redline.
This seems ripe for a Toyota style motor generator on the back for more hp
In a much smaller example Kubota has done this for decades, they take an existing diesel engine and make a gas version. They are about the toughest and longest-lasting gas engines you’ll find in a tractor or mower. Also a bit quieter than most other gassers being that they’re liquid-cooled and inline three cylinders.
kubota engines are fucking brilliant.
I’ve driven a lot of small utility tractors, and the typically clattery engines never really bothered me. But one day a four cylinder Kubota came into the shop, and maaaaaan that thing was smooth. Quiet, too. You could’ve told me it had a Rolls-Royce or Packard engine under the hood instead of a four pot diesel, and I would’ve believed you.
I really hope they stick with gear driven cams like on the ISBs.
Last thing anyone wants to deal with is timing chain(s) on that big of an engine.
I would hope so. Since most of the work they’re doing seems to be in the head and its ancillary systems while keeping the basic block and bottom-end of the diesel, there’d be no reason to lose the timing geartrain.
Cummins has built propane/natural gas versions of the B series for a couple decades now, they’re quite common in spotting tractors.
I’d rather have a godzilla in a class 5/6 truck.
I see a lot of misfueling in the future.
Time to buy stock in fuel pumps and injectors.
Oh my, I never considered that. lol “What do you mean it takes gas? Don’t you see the Cummins badge?!?”
I would imagine that diesel in a gas engine would cause a lot less damage than vice-versa, as gas components are designed for zero-lubricity fuel. Still have to drain and clean the whole system though. A guy here at work fueled up his Super Duty Macho Platinum F250 6.7 with gas and the bill was $17K for the dealer to fix it. He’s kind of a blowhard so we never let him forget it.
At least in my area the nozzles are sized so you can’t put diesel in a gas car. Gas in a diesel is, unfortunately for me once, is possible
The big nozzle diesel pumps are usually only at a station that has a separate diesel-only island. If there’s a diesel pump in with the regular gas pumps it should be the small nozzle variety.
At least that’s been my experience in the Midwest, which I found out after buying my first diesel and thinking it would have a filler that fit the big nozzle diesel pumps.
Even for normal filling islands the diesel nozzle is slightly larger than gasoline. It’s not as big as the single purpose islands that trucks would use but it’s still just big enough so you can’t fill your gas tank with it.
Personally I think it should be the other way around since diesels take more damage when you accidentally put gas in rather than the other way around but with the higher viscosity of diesel and that likelyhood of the average diesel having a larger tank I get why they make the nozzle larger.
Nozzle specs:
Unleaded – no larger than 0.850
Diesel – no smaller than 0.9375 inch
I guess I’ve never actually tried to stick a diesel nozzle in my gas vehicle
¯\_(ツ)_/¯
A few weeks ago a gas station up by Mt Shasta had diesel delivered into the gasoline tanks. About 50 cars filled up and drove off with the wrong fuel.
https://www.motorbiscuit.com/gas-station-sells-diesel-gas-pumps/
My stepdads business partner was one of those 50. It caused quite a bit of damage.
I’m actually surprised that doesn’t happen more often. We have gas and diesel pumps here at work and as the manager, I have to deal with all things related to them – permits, inspections, repairs, etc. At least once or twice a year, a new fuel-delivery driver comes into my office, confused, and asks which fill-tank cover is diesel and which one is gasoline. I would think the green painted cover would be a tip-off, but I’m glad they ask rather than screwing it up.
Maybe a touch of color blindness?
Weird the tanks don’t have different filler ports like the vehicles do to make such mistakes that much harder. The same truck could be used but with the hoses swapped to reflect the fuel.
To be fair, at least around me they will occasionally use green for gas (like E85) and yellow for diesel, so you can’t always trust the color coding.
I’ve noticed that at my local farm stores. For some forsaken reason, their diesel cans are yellow instead of green (though gas is still red). I thought it was fairly universal that gas is red, diesel is green, and ethanol/blend is yellow, but no.
I suppose it could be due to red-green colorblindness, but it’s still a pretty poor solution given that yellow is also used for an entirely different and incompatible fuel.
A manager at my old job filled his company car, a diesel Jag, with petrol.
Everyone in the company took the piss out of him for years.
Cleetus, renowned fuel researcher, tested what ratios of gas/oil would work on a crown Vic attached to a dyno recently. Even with nitrous I don’t think he got much above 50% but more important the engine was undamaged. By oil I mean diesel.
Can I run nitromethane in it? Giddy up.
Yes but only for a few seconds.
CACKLE CACKLE BOOM
Nitropropane is the appropriate additive for petrol and diesel engines.
Is this the beginning of the end for stoplights clouded by fools “rolling coal” on unsuspecting bicyclists?
It can’t happen soon enough.
The new CNG fleet engine. These things will be all over Oklahoma.
At last! A successor to the Ford “300” straight six!
Although it was engineered as a gasoline engine from the get-go, the 300 I-6 shared much in common with diesels in the construction of the (very robust) crankcase and use of gears for timing instead of a typical timing chain. It was nicknamed the “honorary diesel engine” for a reason.
The mechanics at Continental Baking noted that in step vans the Ford 300 six was more reliable than the English Ford and Detroit 53 series Diesels and was almost as easy on cheaper fuel.
Similar situation with the IH 304/345/392 V8’s of the 60’s and 70’s. They also used timing gears and a very robust bottom end and would often go 250K miles at a time when most gasoline engines were done at 100-125K.
The connecting rods are robust enough they were used in race engines.
Obsolete approach now, but still going
Another swap choice for old full sized Kaiser and Jeep pickups.